PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy Surgery: Prior biopsy or subtotal or near-total resection allowed At least 7-10 days but no more than 3 months since prior surgery and/or biopsy Other: No recent methylxanthine-containing medications No concurrent anticoagulants or methylxanthines (e.g., aspirin, nonsteroidal antiinflammatory drugs, warfarin, heparin, theophylline, aminophylline, theobromine) for preexisting medical conditions